Multiple filament electric incandescent lamp



June 6, 1939. I. WARSHAWSKY [2,161,443

MULTIPLE FILAMEN'I ELECTRIC INCANDESCENT LAMP Filed Dec. 16, 1958 Patented Julie 6, 1939 MULTIPLE FILAMENT ELECTRIC 7 INOANDEBCEN'I LAMP lsallorwarshawsky, N. Y., assignor of twenty per cent to Jacob 'Warshawsky and twenty per cent to Nettie Warshawsky, both of Brooklyn, N. "1.

Application This invention relates to improvements in multiple filament electric incandescent lamps, provided with two or more filaments, so that upon destructionof one of the filaments another or reserve filament is automatically brought into operation, thus allowing the further use of the lamp.

Anotherobject of this invention is to provide a novel means of holding one filament, or several, in reserve.

Another object is to provide a novel manner of bringing the reserve filament or filaments into use.

Still another object of this invention is to provide a lamp 01 this character which is simple in construction and therefore inexpensive.

Other objects and advantages will hereinafter appeaa- In the accompanying drawing forming a material part of this disclosure:

Fig. 1 is a schematic diagram of the multiple filament circuit employed inside the bulb of the lamp, (not shown).

Fig. 2' difiers from Fig. 1, in that it shows an additional part for the purpose -of equalizing the amount of light emitted by the main and reserve filaments.

reserve filaments instead of one.

Fig. 4 is a perspective view of a lamp embody 1 ing the invention.

Referring to Fig. 1, the main filament I, consists of parts A and B connected in series to the leads 3 and 4 brought into the bulb,-and which connect outside of the bulb to the current supply:

circuit. The reserve filament 2 'is shunted acros part B of the main filament I.

The reserve filament 2 is designed so that itv requires a lower current for its incandescent operation than main filament I, and it is therefore of smaller cross-section and greater resistance than main filament I.

Part B of main filament I is of slightly smaller cross-section than part'A, but is greater in crosssection than, reserve filament 2. In addition,-

part B of main filament I has only a very small fraction of the length' of part A.

The theory of operation of this multiple filament circuit is as follows:

drop almost equal to the voltage of the supply circuit, while part- B, having only a .very' small December 1c, 1938, Serial 6 Claims. (01. 176-26) ,reserve filament 2. Therefore reserve filament 2 does not, emit any light, and the negligible current through it cannot deteriorate it, and in this way filament 2 is held in reserve.

When main filament I reaches the end of its incandescent life, part B ruptures, and not part A, because as has been stated above, part B is 15 of slightly smaller cross-section than part A, and

therefore operates at a higher temperature.

- Since part B is of weaker construction than part A, and also operates'at a higher temperature, it will rupture before part A of the main filament does; Part A is therefore left electrically intact. when part B ruptures, the virtual short-circuit of the reserve filament 2 is removed, and it now operates in series'with the remaining portion A of mainfilament I. In other words, reserve filament 2 is substituted for part B of main filament I, which has ruptured. Since the resistance of reserve filament'2 is very much greater than that of part B, the current flowing is reduced from its'previous value when the main filament I was intact, This reduced current is sufficient to operate the reserve filament 2 at incandescence, because the reserve filament is designed so that it requires a lower current for its incandescent operation than the main filament I. This reduced current, however, is too low to operate part- A at incandescence, and it therehas a smaller cross-section am a greater resistance than the remaining portion A oi! main filament I, the voltage drop across reserve filament 2 is much greater than that across part A, and is somewhat less than the voltage of the supply circuit due to the voltage drop across part A.

To repeat briefly. when main filament I reaches the end of its incandescent life, part B ruptures,

and the reserve filament 2 is brought into incandescent operation in series with the remaining portion A of main filament I, which remains dark.

Since the remaining-portion A of main filament I, which is in series with the incandescent reserve filament, emits, no light, its iurther deterioration is prevented, and it now serves to connect the reservefilament 2 to the lead I of the lamp,

throughout the incandescent life of-the reserve which is oi weaker construction than part A oi the main filament, so that it will break down or rupture before part A does, when main filament I reaches the end of itsincandescent life. I

Sincethe main filament I has a greater crosssection and a lower resistance than'the reserve filament 2, it allows a greater current to fiow, and it emits a greater amount of light than the reserve filament does when in operation.

If it is desired that the main and reserve filaments shall emit the same amount of light when respectively in operation, thei'ollowing expedients may be adopted: v

The length of part A of main filament l is reduced, and a proper length of resistance wire 5, (see Fig. 2), capable of carrying the current through part A, is inserted in series with part A, between lead 4 and part A of main filament I. This added resistance wire I emits no light or practically none, and the shortened length of part A now emits a reduced amount of light. I! the proper lengths of suitable resistance and filament wire are chosen, the amount of light emitted by parts A and B of main filament I may be made equal tothe amount of light emitted by reserve filament 2, when in operation. The inserted length of 'resistance wire 5 must be capable of holding out during the life of the main and reserve filaments.

Another expedient to ensure that the amount" of light emitted by the main and. reserve filaments shall be equal, is simply to increase the length of part A of main filament I until the added resistance thus secured reduces the amount of light emitted by part A to the point where the amount of light emitted by parts A and B of main filament I is equal to that emitted by reserve filament 2, when in operation.

While only a single reserve filament is shown in Figures 1 and 2, it is to be understood that several reserve filaments may be employed, as illustrated in Fig. '3, which shows three reserve filaments. This is accomplished by connecting the second reserve filament 6 across ashort and weaker portion C of the first reserve filament 2, and the third reserve filamentl is connected across a short and weaker portion D of the second reserve filament 6. i

Each successive reserve filament is designed so that it requires a lower current for its incandescent operation than the'preceding one. Therefore each successive reserve filament has a smaller cross-section and a greater resistance than the preceding one, and consequently the amount of light emitted by'each successive reserve fila- .ment is less than that of the preceding one.

The multiple filament circuit shown in Fig. 3

operates as follows:

When the main filament l reaches the end of its incandescent life, the shorter and weaker portion B which virtually short-circuits the first reserve filament 2 ruptures, and the first reserve filament 2 is brought into incandescent operation,

in series with the remaining portion A of main filament I, which remains dark, due to thereduced current, thus preventing its further deterioration'.

When the first reserve filament 2 reaches the end of. its incandescent life, the. shorter and weaker portion C which virtually short-circuits third reserve filament I is brought into mean-- descent operation, in series with the remaining portions or the 'main filament l, the first reserve filament 2, and second reserve filament 6,'which remain dark, due to the reduced current, thus preventing their further deterioration.

Although I have described my invention with a certain degree of particularity, it is understood that the present disclosure has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and thescope of the invention as hereinafter claimed.

What I claim is:

1. An electric incandescent lamp having a main filament connected to the leads brought inside the bulb, and a reserve filament shunted across, and virtually short-circuited by, a. portion of said main filament of weaker construction and very low resistance, so that when said main filament reaches the end of its incandescent life,

said weaker portion of low resistance ruptures, and the reserve filament is brought into incandescent operation, in series with the remaining portion of the main filament.

2. An electric incandescent lamp having a main filament connected to the leads brought inside the bulb, and 'a reserve filament connected in parallel with a short length of said main fila- -ment of-slightly smaller cross-section, so that when said main filament reaches the end of its incandescent life, said short length of slightly smaller cross-section ruptures, and the reserve filament is brought into incandescent operation, in series with the remaining portion of the main filament.

3. An electric incandescent lamp having a main filament in series with a portion of resistance material of weaker construction and very low resistance, the combination of which is connected to the leads brought inside the bulb, and a reserve filament shunted across, and virtually short-circuited by, said portion of resistance material, so that when said main filament reaches the end of its incandescentfii fe, said resistance material ruptures, and the reserve filament is brought into incandescent operation, in series with the remaining portion of the main filament.

4. An electric incandescent lamp having a main filament connected to the leads brought inside the bulb, and a reserve filament shunted across, and virtually short-circuited by, a portion of said main'filament ofweaker construction and very low resistance, said reserve filament having a smaller cross-section and a greater resistance than the main filament, so that when said main filament reaches the end of its incandescent life, said weaker portion of low resistance ruptures, and the reserve filament is brought into incandescent operation, in series with the remaining portion of the main filament. r

5. An electric incandescent lamp having a main fi ament connected to the leads brought inside 2,161,448 the bulb, and a reserve filament connected in parallel with a short length of said main filament of slightly smaller cross-section, said reserve filament having a smaller cross-section and a greater resistance than the main filament, so that when said main filament reaches the end of its incandescent life, said short length of slightly smaller cross-section ruptures, and the reserve filament is brought into incandescent operation, in series with the remaining portion of the main filament.

6. An electric incandescent lamp having a main filament in series with a portion of resistance material of weaker construction and very low-resistance, the combination of-which is connected to the leads brought inside the bulb, and a reserve filament shunted across, and virtually shortcircuited by, said portion of resistance material, said reserve filament having a smaller crosssection and a greater resistance than the main filament, so that when said main filament reaches the end of its incandescent life, said portion of resistance material ruptures, and the reserve filament is brought into incandescent operation, in series with the remaining portion of the main filament.

ISADOR WARSHAWSKY. 

